There is a wide variety of devices intended to support steel reinforced concrete, which will be integrated inside of the concrete. Its purpose is to separate and provide a predetermined spacing (coatings or concrete layers) to those structural elements among each other, between them and the surface of the form or wooden frame, or between them and the surface of the slabs that make the “mold” for “pouring” the concrete, or the form or wooden frame or any other surface that contains the flow of concrete.
Some examples of such devices, “chairs”, have been described in numerous patents, of which some examples are presented below, whose teachings form part of the state of the art on which the development of this invention is based:
U.S. Pat. No. 5,595,039 (Lowery, 1997) describes a very simplified support device, of the kind of a solid rod with circular cross section vertically oriented, with its upper end being free and designed in order to a rod can lay on it transversely, and the other end being adjusted to a broad circular support base; the device is intended to support a transverse structural element and it permits spacing to be maintained between that element and the surface on which the device is placed, that distance is equivalent to the total height of the device and, therefore, to the thickness of the coating layer; therefore, the structural element has only one point of support in the device.
The device described in U.S. Pat. No. 4,682,471 (Sizemore, 1987), a chair made of molded plastic elements of different sizes forming the letter “A” between them, functions similarly, with the posts placed divergently with a reinforcement element that crosses on the upper part and another on the lower part. The element of minor dimensions is adjusted through the opening of the major element and fits in its place perpendicularly to the major element by specially designed cavities in the respective transversal elements; in this case, the structural element that lays on the crosshead generated in the upper part of the device also has a point of support, although the device seems to offer a better balance by having four points of support.
In U.S. Pat. No. 6,089,522 (Haslem, et al, 2000) and design  patent 421,709 (Haslem, et al, 2000), which refer to the same device, a high chair comprised of four vertical posts joined to one another by a band that runs approximately to half of its height, is described; joint elements are observed between diagonally opposite posts in the upper end, shaping a supporting surface for the structural elements to be supported. The laterals are “H” shaped with their upper ends slightly closer than the lower ends, and the crosshead comprised by the crossbars in the upper part show elements to position the structural element to be supported, so that this element is oriented on one of de diagonals, offering a full line of contact between said structural element and the supporting device (chair); however, to achieve that contact on all the line it is required that the chair be adequately positioned for the diagonal to be collinear with the structural element; otherwise, contact is restricted to only one point.
U.S. Pat. No. 5,729,949 (Hartzheim, 1998) describes a chair used to support and space out meshes of reinforcing bars, wherein it has a cone-shaped hollow body, a flat base that provides great stability, an opening that permits concrete to flow in and around the chair, and pre-shaped notches on the upper part at two levels to keep the bars in the desired position.
US design 334,133 illustrates a chair that has a curved upper end shaped to receive a circular section structural element, the chair rests on four legs with very reduced contact zones and shows a reinforcing ring in the proximity to its base.